As of now, we have no idea what Vader's role in the film will be, or even who will be in the suit. We're hoping that James Earl Jones' iconic voice will return, but nothing has been confirmed.

Rogue One tells the story of the rebels who stole the schematics for the Death Star, which allowed Luke Skywalker and the Rebel Alliance to blow up the Empire's planet-destroyer. It makes sense that Vader, who would have been on the Death Star at the time, would be making an appearance.

We know that Vader probably won't be the main "villain" of the film, though, as Ben Mendelsohn will be playing an Imperial officer named Director Krennic, whom we are expecting to be the hero's primary foil.